Two planes have landed at the presidential wing of Nigeria's Abuja airport hours after government sources said President Umaru Yar'Adua was traveling home from a Saudi Arabian hospital.

Witnesses at the airport say an ambulance was waiting on the tarmac as the planes landed.

There was no immediate word on the condition of the 58-year-old leader who spent the last three months in a Saudi hospital to receive treatment for a heart condition.

Since Mr. Yar'Adua left Nigeria on November 23, he has given only one brief radio interview and made no public appearances.

His absence brought Nigeria to the brink of a constitutional crisis, until parliament installed the president's deputy, Goodluck Jonathan, as acting president this month. Some lawmakers and lawyers have questioned whether that move was constitutional.

Since President Yar'Adua was hospitalized, little information about his health has been released. He was originally reported to be suffering acute pericarditis, a dangerous inflammation of the membrane that covers the heart. Mr. Yar'Adua also has had a chronic kidney ailment.